This invention relates to the art of physical conditioning and more specifically to the principle of isokinetic exercising. This is a combination of isotonic and isometric techniques. This exerciser allows the user to tire a muscle isometrically and then move the tired muscle group isotonically through a complete range of motion at a constant speed.
The principle of friction resistance devices dates back to the nineteenth century when friction resistance brakes were used for fire escapes. (See U.S. Pat. No. 434,888 to Ross and U.S. Pat. No. 779,550 to Leffelman.)
The principle was carried into the twentieth century when several devices were invented to use this principle in exercising. The principle, quite simply, is one of wrapping a rope around a shaft. As the surface area of the rope in contact with the shaft increases by adding more loops or turns, the friction to overcome the drag increases, and the user has to provide more work to overcome the increased load.
Patents involving this principle are set forth as follows: U.S. Pat. No. 3,197,204; U.S. Pat. No. 3,506,262; U.S. Pat. No. 3,510,132; U.S. Pat. No. 3,519,269; and U.S. Pat. No. 3,591,174.